Machine vision lens selection formula

Choosing the right machine vision lens involves a combination of factors that relate to sensor size, field of view, working distance, and application-specific requirements. There is no one-size-fits-all formula for selecting a lens, but here are some common considerations and a basic formula to guide you through the selection process.

Key Considerations

1. Sensor Size: The size of your image sensor is critical in determining the appropriate lens. Common sensor sizes include 1/4 inch, 1/3 inch, 1/2 inch, 2/3 inch, etc. Each sensor size has a specific diagonal length that will affect the lens's field of view.

2. Field of View (FoV): This determines the area covered by the camera at a given distance. A wider field of view requires a shorter focal length, while a narrower field of view requires a longer focal length.

   • Formula for Horizontal FoV: FoV=2×arctan(sensor width2×focal length)FoV=2×arctan(2×focal lengthsensor width​)

   • Formula for Vertical FoV: FoV=2×arctan(sensor height2×focal length)FoV=2×arctan(2×focal lengthsensor height​)

   These formulas help determine the field of view for a given sensor size and focal length.

3. Working Distance: This is the distance between the lens and the object being captured. Knowing the working distance helps in choosing a lens with the appropriate focal length and focus range.

   • Formula for Focal Length: Focal Length=Sensor Size×Object SizeImage SizeFocal Length=Image SizeSensor Size×Object Size​

   This formula helps estimate the required focal length given the sensor size, object size, and image size.

4. Aperture and Light Sensitivity: The lens's aperture affects the amount of light reaching the sensor and the depth of field. A larger aperture (smaller f-number) allows more light and creates a shallower depth of field, useful in low-light conditions and when you want to isolate subjects from the background.

5. Resolution: The resolution required for your application affects the lens choice. Higher resolution sensors need lenses with high resolving power to avoid image degradation.

6. Compatibility: Make sure the lens mount matches your camera's mount. Common lens mounts include C-mount, CS-mount, and others. Additionally, check if the lens has the necessary features (e.g., autofocus, electronic controls) for your application.

Practical Approach for Lens Selection

1. Define Application Requirements: Determine what you need to achieve with the machine vision system. Consider the field of view, resolution, and working distance required for your application.

2. Select Sensor Size: Choose a camera with the appropriate sensor size based on your field of view and resolution requirements.

3. Calculate Focal Length: Using the formulas provided above, calculate the appropriate focal length to achieve your desired field of view at your working distance.

4. Consider Aperture and Light Conditions: Select a lens with an appropriate aperture to suit your lighting conditions and desired depth of field.

5. Check Compatibility: Ensure the lens mount matches your camera's mount, and the lens's physical size fits within your constraints.

By following this approach and considering these key factors, you can select the right machine vision lens for your application. If you have specific requirements, consult with lens manufacturers or machine vision experts for more detailed advice.

FALenses Technology specializes in providing machine vision core hardware. You can go to the official website of FALenses Technology at https://www.falenses.com/ for more information.